175 



PLATE LXIX. 



DYSIDEA PRAGILIS, Johnston. 



Vol. ii, p. 381, ' Mon. Brit. Spongiadse.' 



Fig. 1. A fine specimen of the sponge from the 

 Diamond Ground, off Hastings. Natural size. 



Fig. 2. A specimen located on the back of appa- 

 rently Pisa Gibbsii, Leach. The sponge is in a very 

 fine state of preservation. Natural size. 



Fig. 3. A small well-developed specimen from the 

 rocks off Hastings. Natural size. 



Yol. i, Plate XIV, fig. 271, represents a few fibres 

 of the sponge from a Hastings specimen, exhibiting 

 the mode of the embedment of the sand amid the fibres. 

 X 108 linear. 



Fig. 272 in the same plate represents a single young 

 fibre of the skeleton from the same sponge, exhibiting 

 the manner in which the Keratose fibre picks up and 

 incorporates the single grains of sand in forming its 

 skeleton of extraneous materials. 



